The presumption is that a person who has had the virus, and who recovers, is not a vector of contagion, right? So, everybody retreats to their separate corners. Those who have the virus who are not very sick get better, and stop being a vector of contagion. Those who are very sick get treated, get better or die, and either way are not a vector of contagion. Those who are well are not exposed to the virus, and neither spread it nor contract it. So, the disease runs its course in isolation, and no new cases are created. So, if in a month, there are very few if any new cases, and everybody has stayed away from everybody else, we have three sets of people: 1) dead people, who are not a vector, 2) people who have had the virus, gotten better, and are not a vector, and 3) people who have not had the virus, do not currently have the virus, and are not a vector. But as long as people are out and about, trading microbes, the virus continues to spread, and the number of serious cases that needs to be treated in hospitals continues to rise. The point is to stop at whatever the amount of infection we already have in the the population. We know that things are getting better when the number of new cases drops dramatically. So, again, the end point is when new cases drops dramatically or stops all together. Since the incubation period is about 14 days, a month of very few new cases is probably enough.